A laboratory gets some of its electricity from solar cells that lie on the flat rood of the building. Which single design would most increase the overall efficiency of the solar cells?

• Add solar cells.

• Turn cells to face the sun.

• Place cells at a slant.

• Reflect from other cells.

Bats use echolocation to hunt for food. Echolocation depends on the constant speed of sound and -

• Reflecting from walls

• Refracting from walls

• Time

• Space

What is the current in a copper wire that has a resistance of 2.5 ohms and is connected to a 12-volt electrical source?

• 2.8 amps

• 2.8 volts

• 4.8 volts

• 4.8 amps

The bending of a wave when it crosses from one medium to another is called -

• Reflection

• Diffraction

• Refraction

• Mirroring

How much gravitational potential energy (GPE) does a 5 kg object have when it is 1 meter off the ground?

• 49 m

• 49 J

• 49 watts

• 49 s

What type of wave is this?

• transverse

• standing

• longitudinal

• diffraction

Three identical resistors are connected in series to a battery and a current of 12 A flows from the battery. Which diagram represents the circuit?

• 
• 
• 
• 

Equal drops of red food coloring are added to two cups of water. One cup is very hot, and the other is ice-cold. The color spreads faster in the very hot water. The color spreads faster due to —

• compression

• condensation

• conduction

• convection

A device that converts mechanical energy to electrical energy is a(n) —

• switch

• transformer

• electrical motor

• electrical generator

A metal spoon placed in a cup of hot cocoa becomes hot. Which process transfers heat from the bowl of the spoon to the handle?

• conduction

• convection

• evaporation

• radiation